The phenomena associated with the slide of the plastic sole of a ski over snow are still barely known. Contrary to what may be thought a priori, a totally smooth sole does not slide well over the snow, most probably by reason of the films of water which tend to form on this plastic sole by the friction of the ski over the snow or ice.
This has mot escaped the specialists and a large number of Patents have been filed within the last ten years or so, describing, in ever greater detail, the possible use of skis whose plastic sole, which forms the slide surface, is provided with longitudinal rectilinear scores.
By way of illustration of this state of the art, the following documents may be cited, in chronological order clearly showing the historical development of these proposed skis with grooved sliding sole: CH-A-161.592, AT-A-182.997, FR-A-1.102.116, DE-A-1.108.599, FR-A-2.314.739 and FR-A-2.654.005. In all these documents, the scores are longitudinal and rectilinear.
One highly probable explanation for the use of these scores is that they allow evacuation and break of the films of water which form beneath the sole of the ski when it slides over snow or ice.
It has generally become apparent that the sliding of a ski was strongly influenced by the roughness Ra of its sole, the creation of straight, longitudinal scores having, among other beneficial effects, that of increasing, in manner easily adjustable when machining the sole, the roughness of said sole, all this being, moreover, most probably linked with the above-mentioned phenomenon of formation of films of water beneath this sole.
However, in Applicants' opinion and taking into account the increasing requirements of skiers who are constantly seeking to improve their performances, such straight scores have not appeared to provide an increase in the sliding performances sufficient to satisfy present requirements, particularly in competitive ski-ing.